Pyrolytic carbon has long been known as a very strong, abrasion-resistant material with a great range of variation in properties. Pyrolytic carbon is biocompatible because of its structure and composition, so it has long been used as a material or coating material in medical technology, in particular for producing medical implants of all types. Pyrolytic carbon with a turbostratic structure, optionally including silicon-alloyed carbon microcrystals, is used for coating stents and for the production of artificial heart valves, for example. U.S. Pat. No. 6,569,107 describes carbon-coated intraluminal stents to which the carbon material has been applied by means of chemical or physical vapor-phase deposition methods (CVD or PVD). German Patent DE 3902856 describes molded articles containing pyrocarbon produced by coking of carbon fiber articles, pyrocarbon infiltration and subsequent sealing of the surface with CVD carbon.
The deposition of pyrolytic carbon under PVD or CVD conditions requires a careful selection of suitable gaseous or vaporizable carbon precursors, which are deposited on a substrate at high temperatures, sometimes under plasma conditions, in an inert gas atmosphere or under a high vacuum. In addition, various in vacuo sputtering methods have been described in the state of the art for production of pyrolytic carbon of various structures (see U.S. Pat. No. 6,355,350, for example).
All these prior art methods have in common the fact that the deposition of carbon substrates takes place under extreme temperatures and/or pressure conditions with careful and complicated process control.
Furthermore, because of the different thermal expansion coefficients of the substrate material and the applied CVD carbon layer in the state of the art, frequently only a low adhesion of the layer to the substrate is achieved, resulting in flaking, cracking and a poor surface quality in general.
There has therefore been a demand for methods that are inexpensive and easy to use for coating substrates with a carbon-based material, such that these methods are capable of providing biocompatible surface coatings of a carbon material or carbon-coated substrates for microelectronic applications, for example.
Citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention.